Tax a charge usually of money imposed by authority on persons or property for public purposes.
Taxation can be theft depending upon the goverment handling it. If a government, uses tax for their own pleasures then it can defined as theft. If government officials corrupts the fund and put it in their pocket instead, then it's considered theft. But the not all government are like that, some really uses tax for the improvement of their municipality. For restorations of buildings, for scholarships and etc.